I suggest that you visit your gynecologist to get a professional opinion. Inflammation of the cervix, vaginal infections, Uterus fibroids, & much more can cause pain.
http://www.webmd.com/sexual-conditions/guide/female-pain-during-sex
If you have already been to see your gynecologist, what did he say?

How long is your husbands penis? Many women complain of pain when it is longer than normal.

Another excellent option is to visit Dr. Betty's website that has a great discussion group for women & their sexual problems:
http://dodsonandross.com/

Grizz

my dear, this sounds to be scar tissue adhesions.

having sex post c-section 8 weeks "should" be ok... as long as everything is taken with caution.

What happens when doctors operate - should I say butcher, is they more or less hack through many layers of our bodies. Its not an easy thing, it is very traumatic. Thus our bodies heal in funny ways sometimes....

I would suggest that you partner is not getting caught on you internal per se, but it is along the same meridian as an adhesion inside you and pulling on that area with movement.

There is a supplement that might help... it causes blood thining so be cautious...

Called Serrapeptase. Completely natural silk worm enzyme that helps metabolise needed proteins in the body - such as scar tissue and adhesions.

Research it and see if it is for you. I have recently heard great things about it doing just that.

You can also get an ultrasound to see if there is any internal adhesion to put your mind at ease.

pelvic ultrasound trans abdominal and transvaginal to investigate also the vag vault to make sure there is nothing causing issues there.

all the best...

I had issues too after c-section and emerg. hyst post partum so I can relate... but everything wayyyy better now!

Peace unto you